The reason is that marijuana is still a controlled substance under federal law, raising all sorts off issues for how Colorado and Washington, the other state where voters decriminalized the recreational use of marijuana Tuesday, will implement their initiatives.

“The voters have spoken and we have to respect their will,” Colorado Gov. John Hickenlooper (D) said after the vote. “This will be a complicated process, but we intend to follow through. That said, federal law still says marijuana is an illegal drug, so don’t break out the Cheetos or goldfish too quickly.”

In both states, adults aged 21 and older will be allowed to possess a small amount of marijuana, which will be sold in only state-licensed stores where it will be heavily taxed. For the most part, pot could not be consumed in public. In Colorado, the amendment also allows people to grow a few plants at home.

Colorado and Washington State became the first states ever to make it legal for adults to possess and sell small amounts of pot for recreational use. NBC's Mike Taibbi reports.

Dr. Kevin A. Sabet, former senior drug policy advisor to the Obama administration and director of the Drug Policy Institute at the University of Florida, suggests these results could portend a growing weed war between the feds and the states.

“Once these states actually try to implement these laws, we will see an effort by the feds to shut it down,” Sabet said. “We can only guess now what exactly that would look like, but the recent U.S. attorney actions against medical marijuana portends an aggressive effort to stop state-sponsored growing and selling at the outset.”

The texts of each initiative -- Amendment 64 in Colorado and Initiative Measure 502 in Washington -- make clear that the elimination of penalties for possessing up to an ounce of marijuana if you are 21 or older takes effect after 30 days, once the election results are certified. But the provisions allowing commercial production and sale of cannabis for recreational use require regulations that will be written during the next year in both states.

The Justice Department has so far declined to discuss how the initiatives might function under federal law. Late Tuesday, a spokesman said in an e-mail to NBC News that they were reviewing the Colorado initiative and had no immediate comment.

Sue Ogrocki / AP file

"Don't break out the Cheetos or gold fish too quickly," Colorado Gov. John Hickenlooper (D) said after the marijuana initiative was passed in the state Tuesday.

Obama has cracked down harder on medical marijuana than any president to come before him, argues Rob Kampia, the executive director of the Marijuana Policy Project. In the 17 states where medical marijuana is legal, U.S. attorneys have enlisted the Drug Enforcement Agency and the Internal Revenue Service to take down hundreds of pot shops in just a few short years, Reuters reported.

Three states weighed in on medical marijuana Tuesday with mixed results. Massachusetts voters approved an initiative allowing people to use marijuana for medicinal purposes. In Arkansas, a similar initiative failed. In Montana, voters approved a plan to revamp an existing medicinal marijuana law to make it more restrictive.

Former DEA Chief Peter Bensinger, an outspoken opponent of marijuana legalization, said legalization would lead to an increase in crime and threaten public safety.

“You’ll lose productivity, you’ll have accidents on the highway, you’ll have absenteeism, and you’ll really have a much more weakened society if you have widespread use of marijuana,” Bensinger said.

Still, proponents argue it’s about time pot was made legal and that the war on weed hasn't worked.

“The violence associated with it has become greater, use rates have gone up, the respect toward law enforcement has gone down so the government isn’t achieving any of its stated goals," legalization advocate Allen St. Pierre said.